The Transgenic Animal/Embryonic Stem Cell Shared Facility was initiated in 1991 and became a Cancer Center shared facility in 1995. Its purpose is to provide Cancer Center investigators with pathogen-free transgenic mice with high standards of quality control and efficiency. The service also provides advice and consultation to first-time users, re- derivation of stocks, cryopreservation and associated technologies. Since inception, it has injected 500 genes and 40 ES cell clones including "knock-out" and "knock-in" models. Over 3,5000 founder animals have been provided. Over the past two years, the facility has provided 248 effort days per year with 23 different funded Cancer Center members from five program areas. Increasing volume and sources of revenue has allowed a reduction in charges to investigators from $1,500/project to $750/project in 199. Further expansion of utilization is projected based on institutional expansion of genetics facilities and faculty members.